A charged particle beam device represented by a scanning electron microscope is a device which radiates a charged particle beam such as an electron beam onto a specimen to detect secondary electrons or the like emitted from the radiated position. By detecting the secondary electrons emitted from the specimen, measurement and/or inspection are/is carried out for a semiconductor device or the like. Since the charged particle beam device is a device to radiate particles having charge onto a specimen, if the specimen is charged, the charged particle beam emitted is also affected.
Recently, wafers having fixed charge remaining even if they are grounded have been found in various cases. It is said that causes of such fixed charge are, for example, that due to friction at coating of resist by a spin coater, a substance having polarity in the resist is polarized to fix the potential and that the charge is due to the etching process using plasma (since the fixed charge is charge fixed on the overall surface of the wafer, it will be also referred to as global charge or fixed charge depending on cases in the description below). Further, when the Silicon on Insulator (SIO) technique is employed, since an insulation film is formed on a wafer to form a semiconductor pattern on the insulation film, charge of several hundred volts may take place in some cases.
Patent literature 1 describes a scheme in which the global charge is measured before introducing a wafer into a specimen chamber and a negative voltage to be applied to the specimen is changed based on the measured global charge, to thereby adjust the focus of the electron beam. The scheme to adjust the point of focus of the electron beam by adjusting the voltage applied to the specimen is called retarding focus. This scheme has been described in patent literatures 2 and 3. In addition, a more developed scheme in which the retarding focus is conducted on the basis of quantity of secondary electrons detected by a detector has been described in patent literature 4.